The present invention is directed at a particular problem, the determination of the net or tare weight of a container which contains an unknown quantity of a liquid or of a bulk material which behaves similarly to a liquid. This determination is of practical importance in a number of industries. For example, in the bottled gas industry it is important that the gas container be filled with a proper weight of liquified gas, in order to prevent possible explosion or shortchanging of customers. Since the weights of the containers differ and the containers normally do not arrive empty at the filling machine, it is customary to manually determine the tare weight from an empty weighing which may be noted on the container and to subtract this weight from the final filled weight. The filling process is therefore a relatively slow manual process.
Another example of the need for a weighing system of the type described is in the weighing of precious liquids. Such liquids are normally sold in small bottles of a tare weight which is unknown to the buyer. At present the buyer can confirm the net weight only by placing the liquid in a container of known tare and weighing it.
Vibratory weighing apparatus is known in the prior art, but no such devices have been proposed or used for weighing of liquids and for determining separately the weight of the container and the liquid. Examples of vibratory weighing apparatus are found in the following U.S. Pat. Nos. 3,555,886; 3,967,497; 3,423,999; 3,354,698; and 3,572,098. Conventional tare-weighing apparatus which does not employ vibratory weighing is disclosed, for example, in U.S. Pat. Nos. 3,077,940 and 2,974,863.